Determination of pressure fluctuations in the blading of hydraulic turbines (discussion)
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To obtain the necessary accuracy of investigating an unsteady process in the required range of frequencies o-fmax, Hz, the researcher should fulfill the following conditions: a) there should be no air in the connecting pipe of the sensor; b) to avoid the buffer effect the length of the connecting pipe should not exceed L<356/fmax; c) the natural frequency of the vibrator of the oscillograph should be fb>1.2 fmax at a damping factor of γ=0.6–0.7. In most cases it is necessary to use an amplifier to fulfill this condition; d) analysis of the oscillograph data should be carried out by the method of spectral analysis and supplemented by statistical methods.
On fulfilling the indicated conditions the measurement errors will not exceed 4%; if these conditions are met or if there is a strong frequency background of extraneous fluctuations, the magnitude of the error can increase appreciably.
KeywordsStatistical Method Measurement Error Energy Source Spectral Analysis Power Generation
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